Crawler track



' Dec. 12, 1944.

Filed March 1, 1943 J. A. LAW

CRAWLER. TRACK 2 Sheets-Sheet l gwuwwkw James H. Law

Wag/a Dec. 12, 1944. J LAW 2,364,857

' CRAWLER TRACK Filed March 1, 1943 2 Sheets-Sheet 2 3mm James fLLawPatented Dec. 12, 1944 UNITED STATES PATENT OFFICE 2,364,857 CRAWLERTRACK- James A. Law, Merced, Calif.

Application March 1, 1943, Serial No. 477,517

11 Claims.

This invention relates to endless or crawler track units, either of theself-powered or idler type.

In units of this character it is desirable that the shoes of the tracklink shall have a maximum ground engaging length between the endsprockets or the like, and that the shoe shall follow a definitestraight path between their limits of ground engagement in order totravel smoothly, lessen vibration and avoid the formation of pocketsbetween the track links or their shoes at the ends.

It is also desirable to use the fewest possible links in order to cutdown the number of joints and the accompanying number of parts andwearing elements.

However, even with the relatively short links ordinarily used, theirmounting is such that as one link starts to climb about a sprocket, saidsprocket imparts a downward blow to the adjacent links not yet engagedand climbing. This causes a pounding or binding of the links against thesprocket, with the resultant bumping action and uneven travel andexcessive wear. This is especially evident at the rear end of the track.

With the above facts in mind the objects of my invention are to providea crawler track unit which has a minimum of links; one in which eachlink is well supported while in ground engagement, so as to be veryrigid and stable and thus making the structure a very effective loadcarrier; and one in which there is no knocking or pounding action,kinking or oscillation of the links, and the links travel smoothly andthrough a predetermined fixed path at all times from one end of the unitto the other.

At the same time these advantages are obtained with the use of a shorttrack unit combined with long links, which is favored for certain typesof service.

Essentially the invention consists in arranging and supporting the tracklinks in connection with the end sprockets or similar members of theunit in such a manner that the axis of the pivot pins of the linksfollow a straight line between the sprockets and said line is tangent tothe pitch diameter of the sprockets for the full distance between thepoints of tangency.

A further object of the invention is to produce'a simple and inexpensivedevice and yet one which will be exceedingly effective for the purposefor which it is designed.

'These objects I accomplish by means of such structure and relativearrangement ofparts' as will fully appear by a perusal of thefollowlinks symmetrically positioned relative to the I sprockets.

Figure 2 is a sectional plan on line 2--2 of Fig. 1.

Figure 3 is-a transverse section on the line 3-3 of Fig. 1.

Figure 4 is a plan view of a link detached.

Figure 5 is a fragmentary side elevation of the I unit showing a link asinitially moving up about the adjacent sprocket wheel.

Referring now more particularly to the characters of reference on thedrawings, the crawler track unit in the embodiment here shown, comprisesa pair of spaced side frames I connected at ,intervals by cross bars 2so as to forms.

, rigid structure, and having a central transverse support or hearingmember 3 for the mounting axle 4 about which the unit swivels.

Turnably supported by the frames at one end On the outside is a'pair oftransversely spaced sprocket or track link engaging wheels 5, while asimilar single centrally disposed wheel 6 is sup ported between theframes at the opposite end. The bearing blocks 1 for the wheels areengaged by conventional tightening or take-up devices 8.

If the track structure is driven, the single sprocket wheel wouldpreferably be the drive I sprocket at the rear; the dual sprocket wheelsbeing at the front end. This arrangement main tains the track linksagainst possibl lateral defiection and binding as theycontact theground,

whilekeeping the wear on the drive sprocket and links to a minimum.

An end1ess track extendsbetween and about the wheels, said trackincluding relatively long A links, each of which comprises transverselyspaced rails 9 having'cooperating bosses in at their ends and preferablyflush therewith, and ground engaging shoes ll rigid with the rails andbosses. The bosses serve as supports for the connecting hinge pins P ofthe links and also as wheel engaging members, said wheels, having bossengaging seats or recesses S rather than teeth ofthe normal form. Theseseats are spaced apart the length of the links, and are of coursealldisposed so' as to travel in circular paths concen-;

trio with the axis of rotation of the wheels.

a depressed graduated curvature as at l5.

vided by a guide flange l3 into a pair of transversely separatedportions, the rollers for the most part being dual and straddling theguide flanges; l3 so as to engage the rails on opposite sidesof 1 saidflange, as shown in Fig. 3, so thateach dual" roller is' always engagedwith the flat surface of tangency of the wheels with the pin axis lineA, will always be firmly engaged by one or the other of each roller ofthe dual sets. This feature of course is most necessary on the lower runof the track, since a certain slack along the upper run in relativelyimmaterial.

It will be noted that the rollers are spaced apart a distance equal tohalf the length of a link between pins P, so that each link onthestraightaway is engaged by at leastatworollers, and it is thereforeimpossible for thelinkage": to shift from a straight line position,regardless" of inequalities in the surface engaged.

It may also be noted that while I have'illustrated' and described acertain definite arrangement of wheels, link rails, and rail'engagingrollers; such arrangement may obviously be alteredconsiderablyas.individual installations may justia rail portion. Theendmost rollers [4, however,

are single and engage only one rail portion, and as here shown" eachendmost roller is disposed, at

straight line until the relatively trailing end of such link (or theleading end of the following link) isengaged by a sprocket seat, or sothat the axial line A of the link pins remains tangent to the pitchdiameter line D of the wheel; theroller engaging face of each railportion is formed with This curvature extends from one end fora certaindistance along'the rail and is plotted by atemplate to such a length'anddepth relative to the position of the corresponding end roller l4 andthewheel, as to cause the roller, to ride the bottom ofthe curved railportion and support the. corresponding 'link as it is being lifted bythe wheel until said relatively trailing end of such link passes underthe roller and the latter supports the rail ,of the linkrbeyondto-maintain the link pins in such, straight path.

By reason of this feature, which is the heart of the invention, thedescending boss-engaging elemerits of. a wheel does not contact with alink already. tending to lift, as is otherwise the case, and hencev apounding. and other objectionable action is eliminated.

A. similar link engaging action takes place atj It will be noted thatthe roller engaging curva-,

ture [5 of. the rails extends along the leading or front half ofv onerail portion, and along the trailingor backhalf of the other remainingportion; the remaining roller engaging faces of the rails being flatorstraight.

. The endmost rollers l4 are disposed in proper transverse planes so asto engage corresponding concavities, such rollers at one end being onthe. inside and at the, other end. on. the outside. Also, the rollers l4at the top are disposed in the re-,

verse relation to thoseat the bottom.

Provision is thusmade for properly guiding thev links onto or off of thewheels irrespective of'the direction of travel of thetrack, and alsosupporting the links so that binding strains are taken.

off'the. boss engaging elements of the wheels.

At the same. time the straight track linkage, be-:

tween the turning points or between thepoints of fy without departingfrom the spirit of the invention, which, as stated, is the provision ofa means to maintain thelink p insin. a. straightli e the fulldistancebetweeni and. tangent tothe pitch diameter line of the endwheels about which thev linkage travels.

While I have here shown dual-purposerails.

having a combination. ofiflat and curved roller en-.

gaging faces, it. is obvious thatarail arrangement.

could be provided whereinone rail is utilized sole,- ly for engagementby the endmost. rollers, and

another railv is engaged. solely by. the intermediate rollers.

It ,is also possible to use a single dual purpose. rail instead. of, thetwo shown.

As previously stated; the sprocket wheels ene recesses S1 of wheels 5engage the outer or trailing end bossses ill of the links ahead or whichare already lifted and passing, about thewheels. If,',.

on-the other hand, the track is traveling. toward the left, then thecentral'wheel 61 engages the central bosses IU of the links, which arethen at the trailing' end of the links. In either c'ase' th'e result isthat once a link boss becomesso engaged, there isandcan-be noturning'oi" the boss'in its wheel-recess, as thesprocket rotates anddrives porting frame, rotary members turnably mounted on the frame'atits-ends, an endless track unit extendingabout and between the membersand comprising a plurality of individual links and pivot pinsconnectingthelinks: at adjacent ends for relative fiexingin a vertical plane, themembers including elements. engaging the links passing aboutsaidi'membersi adjacent the link, pins and moving. in circular pathsconcentricjwith the. axes. of: rotation. of the members, the linksbeingrelatively long and. each including a longitudinalrail unit projecting,radially inward, and means engaging. the. rails; of. the

links of the lowerirun of the. track tohold the same against upwarddeflection from a prede' termined' path; said means, and the rails beingarranged to cause the link pins tortravei along a straight line tangentto the circulari-paths oii the members for the full distance between thepoints of tangency'and supporting a link dur-' ing a predeterminedportion of its upward movement about one of the members after therelatively leading end of such link has been engaged by an element ofsaidone member at the lowest pointv of its movement along its circularpath. l I 2. An endless track structure including a supporting frame,wheels turnably mounted on the frame at its ends, an endless track unitextending about and between the wheels and comprising a plurality oflinks, cooperating bosses at the ends of the links and pivot pinsconnecting the bosses and a longitudinal full-length rail unit on eachlink projecting radially inward, the wheels including boss engagingelements movable through circular paths concentric with the axes ofrotation of the wheels, and rollers mounted on the frame and engagingthe rails of the lower run of the track; the rollers and rails beingarranged relative to the wheels to cause the pins of the links of saidlower run to travel in a straight line tangent to the circular paths ofthe wheel elements for the full distance between the points of tangency.4

3. An endless track structure including a supporting frame, Wheelsturnably mounted on the frame at its ends, an endless track unitextending about and between the wheels and comprising a plurality ofrelatively long links, cooperating bosses at the ends of the links andpivot pins connecting the bosses and a longitudinal full-length railunit on each link projecting radially inward, the wheels including bossengaging elements movable through circular paths concentric with theaxes of rotation of the wheels, and rollers mounted on the frame andframe ,at-lts ends, an endless track unit extend,-

lng about and between the wheels and comprising a plurality ofrelatively long llnks, cooper, ating bosses at the ends of the links andplvot, pins connecting the bossesl and 'longltudmal, full-length railsprojecting radially inward, the

wheels lnCluGlng b0SS engaging elementsmovable through circular pathsconcentric with the axes OI rotation oI' the wheels, and means to causethe link-pins along the lower run or the track'to -'follow and remainina straight :lme

cent the opposite end and in the transverse plane of the other endmostroller is formed with a similar concave curvature.

6. A structure as in claim 5 in which the rollers l intermediate theendmost rollers are disposed to engage the rails for, substantiallytheir full math.

I. A structure as in cla1m b, with a longitudinal guide nange projectingradially inward or the track from each rail and laterally separating thecurved portions thereof; the intermediate rollers of the row being dualand straddling said flange.

engaging the rails of the lower run of the track and extending in a rowfor the major distance between the vertical central plane of thewheels;the endmost rollers being disposed a distance from said planes less thanthe length of a link and the adjacent rollers being located from saidplanes a distance substantially equal to the length of a link; each railbeing formed on the surface engageable by an endmost roller so as tohold the corresponding link, when initially engaged at its relativelyleading end and raised at said end by a wheel element upon rotation ofthe corresponding wheel, in such position that the relatively trailingend of said link remains in a plane on a line tangent to said circularpaths until said trailing end reaches the vertical central plane of saidwheel.

4. An endless track structure including a supporting frame, wheelsturnably mounted on the frame at its ends, an endless track unitextending about and between the wheels and comprising a plurality ofrelatively long links, cooperating'bosses at the ends of the links andpivot pins connecting the bosses and a longitudinal full-length rail oneach link projecting radially inward, the wheels including boss engagingelements movable through circular paths concentric with the axes ofrotation of the wheels, and means to cause the link-pins along the lowerrun of the track to follow and remain in a straight line tangent to saidcircular paths for the full distance between the points of tangency;said means comprising a, row of rollers mounted on the frame andengaging the rails, the roller engaging face of each rail for a portionof its length being formed with a concave curvature of predeterminedcontour.

8, In an endless track structure WIllClIl includes a supporting frame,rotary members turnably mounted on the frame at its ends and an endlesstrack unit extending between and about the members and includinga'plurality of links pivoterl together; a plurality of rollers mountedon the frame and engaging, the links of thelower run of the unit, saidrollers being so spaced and arranged that each link not engaged by amember is engaged by at least two rollers while a link as initiallyengaged with a member is also engaged by at least one roller.

9. An endless track structure including a supporting frame, rotarymembers turnably mounted on the frame at its ends, an endless track unitextending about and between the members and comprising a plurality ofindividual links and pivot pins connecting the links at adjacent endsfor relative flexing in a vertical plane, the members including elementsengaging the links passing aboutsaid members adjacent the link pins andmoving in circular paths concentric with the axes of rotation of themembers, the links being relatively long and including a pair oflongitudinal full-length rails projecting radially inward from each linkand forming continuous rows lengthwise of the track and means to causethe link-pins along the lower run of the track to follow and remain in astraight line tangent to the circular paths of the members for the 'fulldistance between the points of tangency; said means comprising a row ofroller units engaging the rails of one row, said rails having flat rail,engaging faces, and endmost rollers engaging the rails of the other row;each last named rail, for each endmost roller, being formed for aportion of its length from adjacent one end with a concave curvature ofpredetermined contour for engagement with the corresponding roller.

10. In an endless track structure, a supporting frame, a single endlesstrack unit comprising a I 5. An endless trackstructureincIuding a5111),, porting frame, wheels turnably mounted on the.

pluralitya-ofi individuazl links, transversexbosses -0n the -links attheir ends and pivot connectionsme-h tweenthe: bosses; a, pair oftransverselyq: spaced; sprocketwheels mountediongthe framefl'at tonerendh aboutw-hichimhe;unitapassesland engaging; the. 5;; bossesadjacenmthe side edges of thalink's, and,

end: bosses; on each: link: ae one end, as-qc.entrally;;-disposeck'b'oss on: each; linliva'fo the: other endz;.an;i

pivot; pins ;.through:. corresponding-bosses: of; achejacentlin'ks:and1connecting the same; ahpaifiofi transverselyspacedwheel'samountedionwtheframea andi having; recesses to; receive; the:transversely? spacedxbosses:ofiithexlinksrandeaboutzzwhichaxthee jtrackunit passes, and a, single wheel mounted:

theefirst named; wheels.and: aboutiwhichgthertracle;

unit,;passes;:. and,;having: recesses-1:0 receive:;.the;;

v cenfinally::disposedbossesmf the*links.;.

JAMESQJAQLAW.

